The present invention relates to a needle control device for stocking knitting machines.
It is known that stocking knitting machines generally comprise a needle holder in which a plurality of slots are arranged side by side, each slot accommodating a needle which can be actuated in order to produce knitting.
The needle holder can be substantially flat, for example as in rectilinear machines, or can be cylindrical, for example as in circular machines.
In some machines, the needles are provided with a heel which protrudes from the slot of the needle holder inside which it is accommodated, so as to engage in appropriately provided paths traced by cams which face the needle holder. In practice, by actuating the needle holder with a continuous or reciprocating motion with respect to the cams or vice versa, the needles travel, with their heel, along such paths and are moved along the slots of the needle holder or maintain a stationary position inside said slots, so as to form stitches or be excluded from knitting, according to the configuration of these paths.
In double-cylinder circular stocking knitting machines, the needle is provided with a double point and has no heels. In this case, the needle is actuated by means of sliders which are accommodated inside the lower needle cylinder and inside the upper needle cylinder, each slider being accommodated in the same slot of the needle holder that accommodates a needle and being provided with a hook which can engage the lower point or the upper point of the needle in order to produce its actuation. The sliders are provided with one or more heels which protrude from the slot of the needle holder inside which they are accommodated so as to engage appropriately provided cams which trace paths for said heels, so as to produce, following the actuation of the needle holder with respect to said cams, the movement of the corresponding needle in order to form stitches. The cams further trace suitable paths for producing the transfer of the needles from the lower needle cylinder to the upper needle cylinder or vice versa.
The needles of stocking knitting machines can also be actuated by means of sub-needles or selectors, each of which is accommodated in a slot of the needle holder which accommodates a needle and faces the end of the needle that lies opposite its point, or faces the end of the slider that lies opposite its end that can engage the needle, in the case of double-cylinder circular machines.
Also these sub-needles or selectors are provided with heels which protrude from the corresponding slot of the needle holder and can engage paths traced by appropriately provided cams which face the needle holder so as to produce the movement of the sub-needle or selector along the corresponding slot of the needle holder in order to produce the actuation of the corresponding needle.
In order to allow the execution of a wide range of knitting types, many of the cams that face the needle holder and trace the paths for the heels of the selectors, of the sub-needles, of the sliders and of the needles in the various machines are provided so that they can move on command toward or away from the needle holder, so as to allow to vary on command, according to a preset knitting program, the path traced for the heels of said elements.
Other selectors are further movable from an inactive position, in which they are inserted, with at least part of their heels, in the corresponding slot of the needle holder, so as to avoid engaging the paths traced by the cams, to an active position, in which they are extracted, with said heels, from the corresponding slot of the needle holder, so as to engage these paths.
The selectors are transferred to the active position or to the inactive position by means of appropriately provided selection devices which face the needle holder, at the selectors, and can be actuated so as to interfere with the selectors so as to vary their position from active to inactive or vice versa.
Although it is thus possible to use two positions, respectively an active position and an inactive position, for the selectors, it is nonetheless necessary, particularly in double-cylinder machines, to use numerous cams which can move toward or away from the needle holder, in order to diversify the paths that must be followed by the heels of the selectors, of the other elements that actuate the needles and of the needles themselves, in order to meet various knitting requirements.
The presence of these movable cams, which is necessary in order to perform the various types of knitting, entails the problem of considerably complicating the structure of the entire machine.
Moreover, the presence of these movable cams forces the provision, on board the machine, of appropriate sensing elements and appropriate control programs in order to prevent, in case of abnormal operation, the cams from being in a position which is not compatible with the position of the heels of is the selectors or sliders or sub-needles or of the needles themselves, which may lead to damage to said heels, forcing to stop the machine in order to replace them.